Herbicidal compositions

ABSTRACT

The invention relates to a composition comprising (a) 2-(2′-nitro-4′-methylsulfonylbenzoyl)-1,3-cyclohexanedione, or an agriculturally acceptable salt or metal complex thereof; and (b) N-isopropyl-(5-trifluoromethyl-1,3,4-thiadiazol-2-yl)-4-(4′-fluoro-oxycetanilide); and their use as herbicides.

This invention relates to new compositions comprising anN-isopropylheteroaryloxyacetanilide herbicide and abenzoylcyclohexanedione derivative, and to their use as herbicides.

The compounds of the invention are known in the art.N-isopropylheteroaryloxyacetanilides are described in European PatentPublication Number 0348737, published on 3 Jan. 1990, which inparticular disclosesN-isopropyl-(5-trifluoromethyl-1,3,4-thiadiazol-2-yl)-(4′-fluoro-oxyacetanilide)as compound 34. Benzoyl cyclohexanediones are described in for exampleEuropean Patent Publication No. 0186118. U.S. Pat. No. 5,506,196,specifically discloses2-(2′-nitro-4′-methylsulfonylbenzoyl)-1,3-cyclohexanedione. Both ofthese publications teach that these compounds possess herbicidalactivity. However, neither of the publications teach specificanti-gramineous properties in the compounds. EP-A1-0348737 teaches thatthe acetanilide compounds may be applied at from 0.01 to 10 kg of activecompound per hectare of soil surface, preferably 0.05 to 5 kg per ha; nodetails of the precise dose rates used for the application of thecompounds to treat graminea. U.S. Pat. No. 5,506,196 teaches that thecompounds of the invention possess high activity in comparison withknown compounds against certain weed species.

Hence the literature does not teach mixtures of these compounds; nordoes it suggest that such a mixture would be expected to be particularlyuseful as an anti-graminicide. At present the most commonly used mixturein this area of weed science comprises metolachlor and atrazine. Theseare frequently recommended for use at dose rates from 1 to 2.5 kg/ha ofmetolachlor and from 0.5 to 2.5 kg/ha of atrazine. An object of theinvention is thus to provide a mixture suitable as a graminicide whichmay be used at reduced dose rates of active compound in comparison withthe known products.

It has been found that the mixture ofN-isopropyl-(5-trifluoromethyl-1,3,4-yl)-4-(4′-fluoro-oxyacetanilide)with 2-(2′-nitro-4′-m thylsulfonylbenzoyl)-1,3-cyclohexanedione provideseffective control of an extremely wide range of both monocotyledon anddicotyledon weeds at reduced dose rates when compared with these knowncompounds. Moreover it provides effective control together withselectivity in important crop species such as maize.

In addition to this, it has been found that in certain conditions thecombined herbicidal activity of2-(2′-nitro-4′-methylsulfonylbenzoyl)-1,3-cyclohexanedione withN-isopropyl-(5-trifluoromethyl-1,3,4-thiadiazol-2-yl)-4-(4′-fluoro-oxyacetanilide)for the control of certain weed species e.g. Setaria viridis,Echinochioa crus-gall, Amaranthus retroflexus and Polygonumlapathifollum, is greater than expected, without an unacceptableincrease. In crop phytotoxicity.

This unexpected effect gives improved reliability in controlling thesecompetitive weeds of many crop species, and contributes to aconsiderable reduction in the amount of active ingredient required forweed control.

According to the present invention there is provided a method forcontrolling the growth of weeds at a locus which comprises applying tosaid locus a herbicidally effective amount of:

(a) a benzoyl cyclohexanedione of formula (I):

which is 2-(2′-nitro-methylsulfonylbenzoyl)-1,3-cyclohexanedione or anagriculturally acceptable salt of metal complex thereof; and

-   -   (b)        N-isopropyl-(5-trifluoromethyl-1,3,4-thiadiazol-2-yl)-4-(4′-fluoro-oxyacetanilide)        having the formula (II):        For convenience        N-isopropyl-(5-trifluoromethyl-1,3,4-thiadiazol-2-yl)-4′-(4′-fluoro-oxyacetanilide)        is hereafter referred to as compound B.

The amounts of 2-(2′-nitro-methylsulfonylbenzoyl)-1,3-cyclohexanedioneand compound B applied vary depending on the weeds present and theirpopulation, the compositions used, the timing of the application, theclimatic and edaphic conditions, and (when used to control the growth ofweeds in crop growing areas) the crop to be treated. In general, takingthese factors into account, application rates from 0.5 g to 512 g ofbenzoyl cyclohexanedione and from 10 to 10000 g of compound B perhectare give good results. However, it will be understood that higher orlower application rates may be used, depending upon the problem of weedcontrol encountered.

The method of the invention is most preferably used for the control ofweeds at a locus used, or to be used for the growing of a crop. Whenapplied to a crop-growing area, the rate of application should besufficient to control the growth of weeds without causing substantialpermanent damage to the crop.

Crops which the mixture may be used with include soyabeans, sugarcane,cotton, maize, sunflower, peas, chickpeas, potatoes, sorghum rice andcereals. The preferred crop, in terms of the selectivity of the mixture,is maize. For the selective control of weeds at a locus of weedinfestation which is an area used, or to be used, for growing of cropsapplication, rates from 5 g to 512 g of benzoyl cyclohexanedione andfrom 50 to 5000 g of compound B per hectare are particularly suitable,preferably from 20 g to 200 g of benzoyl cyclohexanedione and from 80 gto 875 g of compound B per hectare, most preferably from 25 g to 150 g(about 80 g being most preferred) of benzoyl cyclohexanedione and from300 g to 500 g (360 g being most preferred under humid conditions and450 g under more dry conditions) of compound B per hectare.

The mixture is preferably applied pre-emergence but can also be appliedpost-emergence (especially at an early stage of weed growth). By theterm ‘pre-emergence application’ is meant application to the soil inwhich the weed seeds or seedlings are present before emergence of thecrop. One example of a pre-emergence application is known as ‘pre-plantincorporated’ (PPI), where the herbicide is incorporated into the soilbefore planting the crop. Early PPI application may also be used. Themixture may also be applied pre-planting (i.e. before the crop isplanted) either to the surface of the soil or soil-incorporated. Earlypre-plant treatments using the mixture (particularly surface applied)are also a feature of the method of the invention.

According to a further feature of the present invention there areprovided herbicidal compositions comprising:

-   -   (a) 2-(2′-nitro-4′-methylsulfonylbenzoyl)-1,3-cyclohexanedione        or an agriculturally acceptable salt or metal complex thereof;        and    -   (b)        N-isopropyl-(5-trifluoromethyl-1,3,4-thiadiazol-2-yl)-4-(4′-fluoro-oxyacetanilide);        in association with, and preferably homogeneously dispersed in,        a herbicidally acceptable diluent or carrier and/or surface        active agent.        The term “herbicidal composition” is used in a broad sense, to        include not only compositions which are ready for use as        herbicides but also concentrates which must be diluted before        use. Preferably, the compositions contain from 0.05 to 90% by        weight of benzoyl-1,3-cyclohexanedione and compound B.        Unless otherwise stated, the percentages and ratios appearing in        this specification are by weight.

Generally a composition in which the ratio of (a):(b) is from 1:20000 to50:1 wt/wt (or from 1:20000 to 51.2:1 wt/wt) is used, proportions from1000:1 to 10:1 wt/wt (or from 1000:1 to 10.24:1 wt/wt) being preferred,with proportions from 1:45 to 2.5:1 wt/wt (or from 1:43.75 to 2.5:1wt/wt) being more preferred, and proportions from 1:20 to 2:1 wt/wtbeing especially preferred; ratios of 1:14 to 1:16 wt/wt (or of about1:14 wt/wt) in humid conditions and of 1:17 to 1:20 wt/wt (or of about1:18 wt/wt) in dry conditions being most preferred.

The preferred formulation according to the invention is in the form of awater dispersible granule, although it will be understood that otherformulation types known in the art may also be used.

In accordance with the usual practice, a tank mix may be prepared priorto use by combining separate formulations of the individual herbicidalcomponents.

According to a further feature of the present invention, there isprovided a product comprising:

-   -   (a) 2-(2′-nitro-4′-methylsulfonylbenzoyl)1,3-cyclohexanedione or        an agriculturally acceptable salt or metal complex thereof; and    -   (b)        N-isopropyl-(5-trifluoromethyl-1,3,4-thiadiazol-2-yl)-4-(4′-fluoro-oxyacetanilide);        as a combined preparation for simultaneous, separate or        sequential use in controlling the growth of weeds at a locus.

The following non-limiting experiments illustrate the present invention.

Experiment 1

Seed of various broad-leaf and grass weed species were sown inunsterilised clay loam soil. The soil surface was then sprayed withranges of concentrations of either the individual herbicide or mixturesof the two herbicides in various proportions dissolved in a mixture ofacetone and water. The said weeds are Abutilon thophrasti, Amaranthusretroflexus, Chenopodium album, Digitaria sanguinalis, Echinochloacrus-galli, Ipomoea lacunosa, Panicum millaceum, Polygonum convolvulus,Polygonum lapathifollum, Setaria faberi, Setaria viridis, Sorghumvulgare and Xanthium strumarium.

Two weeks after treatment the percent reduction in plant growth,compared to an untreated control, was assessed.

Experiment 2

Seed of various weed species, as listed in Example 1, were sown andgrown up to a 1-3 leaves stage. Post-emergence applications of a rangeof concentrations of either the individual herbicide or mixtures of twoherbicides in various proportions dissolved in a mixture of acetone andwater were made.

Two weeks after treatment the percent reduction in plant growth,compared to an untreated control, was assessed.

In both cases an effective level of weed control against a number ofweed species, at substantially reduced application rates of activeingredient was observed.

1. A method for controlling the growth of weeds at a locus whichcomprises applying to said locus a herbicidally effective amount of: (a)2-(2′-nitro-4′-methylsulfonylbenzoyl)-1,3-cyclohexanedione or anagriculturally acceptable salt or metal complex thereof; and (b)N-isopropyl-(5-trifluoromethyl-1,3,4-thiadiazol-2-yl)-4′-(4′-fluoro-oxyacetanilide)having the formula (II):


2. The method according to claim 1 using an application rate of from 0.5g to 512 g per hectare of2-(2′-nitro-4′-methylsulfonylbenzoyl)-1,3,4-cyclohexanedione and from 10to 10000 g per hectare ofN-isopropyl-(5-trifluoromethyl-1,3,4-thiadiazol-2-yl)-4-(4′-fluoro-oxyacetanilide).3. The method according to claim 1, wherein the locus is used, or to beused, for the growing of a crop.
 4. The method according to claim 3wherein the crop is maize.
 5. The method according to claim 1, whereinfrom 5 g to 512 g per hectare of2-(2′-nitro-4′-methylsulfonylbenzoyl)-1,3-cyclohexanedione and from 50 gto 5000 g per hectare ofN-isopropyl-(5-trifluoromethyl-1,3,4-thiadiazol-2-yl)-4-(4′-fluoro-oxyacetanilide)are applied to said locus.
 6. The method according to claim 1, whereinfrom 20 g to 200 g per hectare of2-(2′-nitro-4′-methylsulfonylbenzoyl)-1,3-cyclohexanedione and from 80to 875 g per hectare ofN-isopropyl-(5-trifluoromethyl-1,3,4-thiadiazol-2-yl)-4-(4′-fluoro-oxyacetanilide)are applied to said locus.
 7. The method according to claim 1, whereinfrom 25 to 150 g per hectare of2-(2′-nitro-4′-methylsulfonylbenzoyl)1,3-cyclohexanedione and from 300to 500 g per hectare ofN-isopropyl-(5-trifluoromethyl-1,3,4-thiadiazol-2-yl)-4-(4′-fluoro-oxyacetanilide)are applied to said locus.
 8. The method according to claim 1, wherein(a) and (b) are applied to said locus by pre-emergence application.
 9. Aherbicidal composition comprising: (a)2-(2′-nitro-4′-methylsulfonylbenzoyl)-1,3-cyclohexanedione or anagriculturally acceptable salt or metal complex thereof; and (b)N-isopropyl-(5-trifluoromethyl-1,3,4-thiadiazol-2-yl)4(4′-fluoro-oxyacetanilide);in association with a herbicidally acceptable diluent or carrier and/orsurface active agent.
 10. The composition according to claim 9 in whichthe weight ratio of (a):(b) is form 1:20,000 to 55:1.
 11. Thecomposition according to claim 9 in which the weight ratio of (a):(b) isfrom 1:1000 to 10:1.
 12. The composition according to claim 9 In whichthe weight ratio of (a):(b) is from 1:45 to 2.5:1.
 13. The compositionaccording to claim 9 in which the weight ratio of (a):(b) is from 1:20to 2:1.
 14. The composition according to claim 9, wherein saidcomposition is in the form of a water dispersible granule.
 15. A productcomprising a herbicidally effective amount of: (a)2-(2′-nitro-4′-methylsulfonylbenzoyl)-1,3-cyclohexanedione or anagriculturally acceptable salt or metal complex thereof; and (b)N-isopropyl-(5-trifluoromethyl-1,3,4-thiadiazol-2-yl)-4-(4′-fluoro-oxyacetanilide);as a combined preparation for simultaneous, separate or sequential usein controlling the growth of weeds at a locus.